What is the recommended method for collecting and preserving liquid blood stains?

The recommended method for collecting and preserving liquid blood stains involves using a gauze pad to absorb the liquid blood and then freezing it. This method is effective because freezing helps preserve the integrity of the biological evidence, preventing degradation and potential contamination over time.

Collecting liquid blood stains with a gauze pad ensures that you are removing the surrounding liquid effectively, while freezing it minimizes the risk of bacterial growth and other factors that could compromise the sample during storage. This approach aligns with forensic best practices for handling biological evidence, particularly in maintaining the viability of DNA analysis and other forensic examinations that may be necessary during an investigation.

In contrast, other methods may not effectively preserve the evidence. For instance, air drying blood on clothing can lead to contamination or degradation of the sample as it may attract bacteria or other environmental factors. Storing in plastic can create a moisture trap, which encourages bacterial growth. Wiping with a moistened cloth or soaking with paper towels can alter the sample's composition, potentially compromising its usefulness in forensic analysis. Therefore, the choice to freeze blood stains collected with gauze is the best practice in forensic contexts.